The invention relates in general to waste disposal devices and disposal methods and to a new and useful installation for low-temperature carbonization of waste and impure materials under the exclusion of air with a low-temperature carbonization cylinder, and in particular to a device for after-burning of residual materials from the low-temperature carbonization installation.
Low-temperature carbonization installations for the waste removal of household and industrial waste and the like are known, for example from DE-PS 24 32 504. In such low-temperature carbonization installations, through pyrolysis, a thermal treatment of waste takes place, which ensures gain of basic materials while placing the least possible stress on the environment and converting the solid waste into a gaseous fuel which is readily burnable. Pyrolysis, hence, is a method of dry distillation which is carried out in an oxygen-free atmosphere.
A low-temperature carbonization installation is described, for example in "VGB Kraftwerkstechnik" (VGB Power Plant Technology) 66, No. 5, May 1986. In this installation unsorted household garbage is reduced in size and introduced via a feed system into an indirectly heated rotating cylinder. In a heating gas generator a part of the generated pure gas is burned. The originating gas fumes are carried together with exhaust gases of a gas motor through the heating gas pipes of the rotating cylinder. The garbage is heated to approximately 500.degree. C. At this temperature and a dwelling time of the garbage of 60 to 90 minutes the garbage is degassified. Non-ferrous and heavy metals are not oxidized since in the rotating cylinder a reduced water vapor/ammonia atmosphere obtains. At the discharge end of the rotating cylinder the gaseous and the solid stream of matter are separated. The residual material is carried off via a discharge system. Following the treatment of the garbage in the low-temperature carbonization cylinder is the treatment of the low-temperature carbonization gases in the gas converter and the gas purification.
The residual materials which are discharged from the low-temperature cylinder contain, as a rule, still a high fraction of combustibles in the form of carbon, specifically approximately 5 to 20 percent by weight. Long-term experiments, with respect to the ability of these carbon-containing residual materials to be deposited in a dump, have shown that the deposition in terms of the danger of spontaneous combustion is not critical.
For the energy household of the low-temperature carbonization installation, however, reducing the carbon fraction in the residual material would be desirable in order to be able to compete economically with other methods, for example garbage burning. 50% of the energy contained in garbage is today utilized for the internal requirement of the garbage burning installation and only 50% are utilized as energy output (heat flow). Here, however, the goal is to improve the ratio of internal energy requirement to energy release in favor of energy release.